Luminaire and lamellae louver therefor

ABSTRACT

A luminaire has side reflectors having edges defining the width W of a light-emission window, and a plurality of lamellae, which have a concave outer edge in the light-emission window and an inner face remote from that window. In the centers of the lamellae, the lamellae have a distance h o  between the outer edge and the inner face that is &lt;0.1 W. As a result, the total surface area of the inner face is relatively small. Internal reflections are thereby reduced, and a higher light output is obtained. If the lamellae are solid and made of plastic, less material is required for their fabrication. In a preferred embodiment, h o &lt;0.05 W, and the inner face may then be convex and even have the same contour as the outer edge. The lamellae louver has lamellae of h o &lt;W, in which W is also the length of the lamellae.

The invention relates to a luminaire provided with:

a light-emission window of a width W;

elongate side reflectors, mounted opposite each other, equidistant froma plane P that is at right angles to the light-emission window, whichside reflectors have an edge defining the width W of the light-emissionwindow;

means for accommodating an electric lamp between the side reflectorsalong the light-emission window;

a plurality of substantially parallel, substantially equidistantlamellae transverse to plane P, the lamellae having V-shapedcross-sections and,

which lamellae have a concave outer edge in the light-emission window,an inner face remote from the light-emission window, a distance h_(o)between the outer edge and the inner face in plane P, and flanks fromthe outer edge to the inner face.

The invention also relates to a lamellae louver comprising a pluralityof substantially parallel, substantially equidistant, interconnectedlamellae with a V-shaped cross-section having:

a length W;

a concave outer edge in a light-emission window;

an inner face remote from the light-emission window; and

flanks extending from the outer edge to the inner face; and, in a centerof a lamella, a distance h_(o) between the outer edge and the innerface.

An embodiment of such a luminaire is known from EP-A-0 757 772.

The function of the side reflectors is to collect the light generated byan accommodated lamp into a beam and furthermore, to create a shieldingangle, within which the lamp is not visible. The shielding angle extendsin a plane at right angles to the edge of the side reflectors, the C₀plane, from a plane S through the edges of the side reflectors. Thisshielding angle is especially important in spaces where monitors areused, in order to prevent annoying reflections. The side reflectors alsoprovide screening in planes surrounding the C₀ plane.

The lamellae have a similar shielding function in plane P, which is alsocalled the C⁻⁹⁰ plane, and the planes surrounding it. To achieve that asimilar shielding is obtained in said surrounding planes, the outer edgeof the lamellae is concave. The said distance h_(o), the height of thelamella in situ, and the interspacing of the lamellae decide the size ofthe shielding angle in plane P given by the lamellae. The shieldingangle α, see FIG. 1 showing a cross-section of lamellae 10 in plane P,decreases when the interspacing of the lamellae 10 is increased from dto D, and when the height is reduced from H₀ to h_(o).

The side reflectors and the lamellae work together to create a shieldingangle around the luminaire, within which the lamp accommodated is notdirectly visible.

In general, the side reflectors are shaped in such a way that theyconcentrate light coming straight from the lamp into a beam, andconsequently reflect it outside the shielding angle.

The lamellae may have concave flanks in plane P, and also next to thisplane, in order to reflect incident light in the beam, at a greaterangle to plane S than the angle at which the light falls onto thelamellae. In that case, the luminaire can be used in spaces withmonitors, because the lamellae also prevent radiation of light in theshielding angle. Alternatively, the lamellae may have flat flanks inplane P, and also next to this plane, which—since the lamellae have aV-shaped cross-section—reflect incident light at a greater angle toplane S than the angle of incidence.

In the known luminaire, the lamellae either have a straight inner face,which is profiled in the case of specular or semi-specular lamellae, oran inner face ascending towards the side reflectors. The purpose of theprofile or the ascending inner face is to ensure that light shed ontothe inner face by the lamp is reflected by the inner face to a locationof the side reflectors situated deeper in the luminaire. This is toprevent the occurrence of annoying bright spots of light reflected bythe inner face and subsequently by the side reflectors within theshielding angle.

The lamellae have another additional function, which is fulfilled by theflanks due to the fact that the inner face is straight or even ascendstowards the side reflectors, and the fact that the flanks extend as faras the inner face. The lamellae thus obviate clear mirror images of theaccommodated lamp being observed in the side reflectors from theshielding angle, at the angles in the range from ca 30°–40° to plane P,in which those mirror images originate. This is illustrated in FIGS. 2and 3.

FIG. 2 shows a section of a luminaire, viz. a side reflector 2 withthree lamellae 10 in perspective view. One zone of the side reflector,which is visible above the lamella that is at the front in FIG. 2, inthe position shown, produces mirror images of the burning lampaccommodated within the shielding angle, where the observer of theluminaire is located. This zone is not visible above the central andrearmost lamellae, because the flanks 13 of the lamellae cover the zonecorrectly in those places. This happens although the outer edges 11 ofthe lamellae are concave and are therefore much closer in theperspective view shown to the inner face 12 (which is, after all, theboundary of the flank of the adjacent lamella) than if the lamellae wereto have a straight outer edge, as indicated by the broken line.

FIG. 3 shows a section of another luminaire in perspective view. In thisluminaire, the lamellae 10 are plates with a concave outer edge 11. Theinner edge 12′ is not concave, owing to the fact that the lamellae donot ascend towards the side reflectors. The inner edge is not evenstraight, but is convex, and of the same curvature as the outer edge. Asa result of the convex inner edge, the lamellae no longer complement oneanother—which is the case in FIG. 2—and do not screen the zone of theside reflector above the lamellae. The observer can see clear mirrorimages of the lamp from the shielding angle. The luminaire shown istherefore not suitable for use in spaces where monitors are used.

A drawback of the known luminaire is that the inner face of the lamellaehas a relatively large surface area, and is exposed to a relative largeluminous flux from the accommodated lamp. This leads to additionalreflections on the side reflectors. Reflections in the luminaire cause aloss of light, because materials absorb a fraction of the incidentlight.

It is a first object of the invention to provide a luminaire of the kinddescribed in the opening section which allows relatively few reflectionson the inner faces.

A second object of the invention is to provide a lamellae louver of thekind described in the opening section which allows relatively fewreflections on the inner faces when used in a luminaire.

It has been found by experiment that the first object according to theinvention is realized in that h_(o)<0.1 W. Since relatively fewreflections occur on the inner faces, the loss of light is counteracted,and the luminaire has a relatively high efficiency.

If, in a luminaire with a chosen shielding angle, which, as mentioned,is determined transverse to plane P by the edge of the side reflectorsand the position of the lamp—so by the position of the means foraccommodating the lamp—the lamellae have, according to the invention,the small value of h_(o) mentioned above (the dimension h_(o) also beingreferred to here as height), they are situated at a greater distancefrom the accommodated lamp, and the inner face of each lamella istherefore within a smaller angle as seen from the lamp, so that thelamella is hit by less light and fewer reflections take place on it.Furthermore, the lamellae—which have a V-shaped cross-section—have arelatively small height, so that the flanks will be less far apart fromthe outer edge, and the inner face has a relatively small width, cf.FIG. 4. In FIG. 4, β1 is the angle within which light from a point ofthe lamp is hits the inner face of a lamella 10 in a conventionalluminaire, β2 is the angle within which this happens if the inner faceof the lamella were to be at a greater distance from the lamp, and β3 isthe angle concerned in a lamella of the luminaire according to theinvention, in which the flanks 13 are at the same angle. FIG. 4diagrammatically shows the differences with lamellae with flat flanks,but if the flanks are concave, which is often the case, the width of theinner faces increases more than linearly with increasing height. If theluminaire according to the invention is provided with lamellae withconcave flanks, the relative size of β3 is even smaller.

It is noted that h_(o) is about 0.2 to 0.4 W in conventional luminaries.

FIG. 5, representing a section of the luminaire according to theinvention, the section being analogous to and in a position analogous toFIG. 2, shows that the lamellae 10 completely screen the area of theside reflectors 2 in which mirror images of the lamp can be visible.Even sections that are located relatively far away from the edge of theside reflector, between the lamellae, which are still unscreened in FIG.2 and in which mirror images may still be visible, are screened in FIG.5. In FIG. 5, contrary to FIG. 2, the part of the side reflector that isstill visible is only very small. This is an important advantage of theluminaire according to the invention.

The lamellae may be shaped from plate material, e.g. from specular orsemi-specular material, for example from aluminum. Alternatively, thelamellae may be shaped from plastics. They may be translucent fordecorative applications, or non-translucent. They may be white, forexample, or reflectorized. If the luminaire according to the inventionis provided with plastic lamellae, there is another advantage in thatthe amount of material used to build the lamellae is smaller than in aconventional luminaire.

It is favorable for the amount of material used to build the lamellae ingeneral, so also for lamellae made of plate material, if the inner faceis substantially straight. In this case, the inner face does not ascendtowards the side reflectors, but runs basically parallel to plane S.

In a special embodiment, h_(o)<0.05 W in the luminaire. The inner facemay then be convex, as was also found by experiment. When comparing FIG.5 with FIG. 2, it is clear that in the case of the lamellae with smallheight, the small h_(o) of FIG. 5,—which are closer together to providethe same screening as in FIG. 2—it is no longer the center of the outeredge 11 that works together with an end of the flank 13 to screen theside reflector, as in FIG. 2, but is a section of the outer edge lyingmuch closer to the side reflector, where the outer edge lies closer toplane S through the edges of the side reflectors. The flanks of thelamellae may then even have the same contour on the inner face 12 as onthe outer edge. In this way, a further saving of material is realized.In general, h_(o) is greater than 0.03 W, because of the form-retainingproperties of the lamellae.

To create a light beam of high quality, it is favorable if the lamellaeare specular and the inner face is profiled, in order to reflectincident light to places of the side reflector that are locatedrelatively deep in the luminaire. In the case of lamellae made of sheetmetal, this profile may, for example, comprise tongues pressed inwardsor outwards from the inner face. In the case of lamellae made ofplastics, the inner face may, for example, have a stepped structure.

The lamellae may be connected inseparably to the side reflectors.Alternatively, the lamellae may be interconnected into a louver, to forma lamellae louver according to the invention.

The luminaire may be destined for use with one or more linearfluorescent lamps, or with one or more fluorescent lamps having two ormore essentially parallel lamp-vessel parts. The side reflectors mayextend together around an accommodated lamp, and be integrated.

The second object of the invention is realized in that h_(o)<0.1 W. Therest of what has been explained above with respect to the luminaireaccording to the invention similarly applies to the lamellae louver.

The lamellae of the louver may, for example, be interconnected by meansof strips that extend transverse to the lamellae, and in the case of alouver mounted in a luminaire, they may lie, for example, be near oragainst a respective side reflector. Such a louver is especiallyattractive if it is made of plastic, because in that case it can be madeof one piece and there is no need for positioning the lamellae relativeto one another, thus avoiding a considerable effort in mounting thelamellae.

The invention, an embodiment of the luminaire and of the lamellae louveraccording to the invention, is shown in the drawings and explained.

FIG. 1 shows lamellae in cross-section through their centers;

FIG. 2 shows a section of a luminaire, not according to the invention,in perspective view;

FIG. 3 shows a section of another luminaire, not according to theinvention, in perspective view;

FIG. 4 shows a lamp in side elevation with lamellae in cross-section;

FIG. 5 shows a section of an embodiment of the luminaire according tothe invention in perspective view;

FIG. 6 shows another embodiment of the luminaire according to theinvention in cross-section;

FIG. 7 shows the luminaire of FIG. 6 viewed along VII in FIG. 6;

FIG. 8 shows an embodiment of the lamellae louver according to theinvention, in a position corresponding to that of FIG. 7;

FIG. 9 shows the lamella of an embodiment, other than that shown inFIGS. 5 to 8, in front elevation;

FIG. 10 shows one half of the lamella of FIG. 9 in perspective view.

Corresponding components have been given the same reference numeralsthroughout the Figures.

FIGS. 1–5 have been explained above.

In FIGS. 6 and 7, the luminaire has a light-emission window 1 of a widthW. Elongate side reflectors 2 are placed opposite each other,equidistant from a plane P that is at right angles to the light-emissionwindow 1. The side reflectors 2 have an edge 3, which determines thewidth W of the light-emission window 1. Means 4 are provided foraccommodating an electric lamp 1 s between the side reflectors 2 alongthe light-emission window 1. A plurality of substantially parallel,substantially equidistant, lamellae with a V-shaped cross-section arepositioned transverse to plane P. The lamellae 10 have a concave outeredge 11 in the light-emission window 1, an inner face 12 remote from thelight-emission window 1, a distance h_(o) between the outer edge 11 andthe inner face 12 in plane P, and flanks 13 extending from the outeredge 11 to the inner face 12. The luminaire has a housing 9.

In the luminaire shown: h_(o)<0.1 W.

A plane S passes through the edges 3 of the side reflectors 2. A ray oflight leaving from the circumference of the accommodated lamp, astraight tubular fluorescent lamp in the luminaire shown, and justmissing an edge encloses a shielding angle α with plane S. In plane P,the lamellae 10, cf. FIG. 1, give the same shielding angle. The lamellae10 give the same screening in planes on both sides of plane P; the sidereflectors also give screening in planes around the plane of thedrawing, FIG. 6.

The inner face 12 is substantially straight. It runs parallel to planeS.

The lamellae 10 reflect light specularly and the inner face 12 isprofiled by means of tongues 15 cut loose from the inner face 12 andpressed inwards.

The side reflectors 2 and the lamellae 10 in FIGS. 6 and 7 form anintegral whole and are assembled from aluminum parts.

In the section of an embodiment of the luminaire of FIG. 5 the lamellaehave h_(o)<0.05 W. The inner face 12 of the lamellae 10 is convex.

The lamellae louver of FIG. 8 has a plurality of substantially parallel,substantially equidistant, interconnected lamellae 10 with a V-shapedcross-section and of a length W. The lamellae 10 are interconnected bymeans of strips 17, which are interconnected by means of cross strips18. The lamellae 10 have a concave outer edge 11 in a light-emissionwindow 1, see FIG. 9, and an inner face 12 remote from thelight-emission window 1. Flanks 13 extend from the outer edge 11 to theinner face 12. In their center 14, the lamellae 10 have a distance h_(o)between the outer edge 11 and the inner face 12.

In this case the following applies: h_(o)<0.1 W. In the embodimentshown, h_(o)<0.05 W also applies.

The inner face 12 is convex and has the same curvature as the outer edge11 in FIG. 9.

The lamellae 10 are specular and the inner face 12 is profiled, as canbe seen from FIG. 10.

The louver of FIG. 8 is made of plastic and forms one integral whole,which is formed in a mold and then aluminized to produce a mirrorfinish.

1. A luminaire provided with: a light-emission window of a width W;elongate side reflectors, placed opposite each other, equidistant from aplane P that is at right angles to the light-emission window, which sidereflectors have an edge defining the width W of the light-emissionwindow; means for accommodating an electric lamp between the sidereflectors along the light-emission window; a plurality of substantiallyparallel, substantially equidistant lamellae with a V-shapedcross-section, transverse to plane P, which lamellae have a concaveouter edge in the light-emission window, an inner face remote from thelight-emission window, a distance h₀ between the outer edge and theinner face in plane P, and flanks from the outer edge to the inner face,wherein h₀<0.1 W.
 2. A luminaire as claimed in claim 1, wherein theinner face is substantially straight.
 3. A luminaire as claimed in claim1, wherein h₀<0.05 W.
 4. A luminaire as claimed in claim 3, wherein theinner face is convex.
 5. A luminaire as claimed in claim 2, wherein thelamellae are specular and the inner face is profiled.
 6. A lamellaelouver for a luminaire, the luminaire having a light emission window,the lamellae louver comprising a plurality of substantially parallel,substantially equidistant, interconnected lamellae with V-shapedcross-sections, having: a length W; a concave outer edge capable ofbeing mounted in the light-emission window; an inner face remote fromthe light-emission window when the lamellae louver is installed in theluminaire; flanks extending from the outer edge to the inner face; andin a center of one of said flanks, a distance h_(o) between the outeredge and the inner face, wherein h₀<0.1 W.
 7. A lamellae louver asclaimed in claim 6, wherein the inner face is substantially straight. 8.A lamellae louver as claimed in claim 6, wherein h₀<0.05 W.
 9. Alamellae louver as claimed in claim 8, wherein the inner face is convex.10. A lamellae louver as claimed in claim 7, wherein the lamellae arespecular and the inner face is profiled.